In the end, we can find available themes for CSS to use. I pick up base16.solarized.dark theme to generate CSS file for my test site syntax highlighting.

rougifystylebase16.solarized.dark>css/syntax.css

And I include this generated CSS file into markdown file:

<linkhref="/test/css/syntax.css"rel="stylesheet">

Now we can see the corresponding languages are highlighted by Rougehere.

Using Rouge is one way for syntax highlighting. It comes together with Jekyll as Ruby gems and get supported by GitHub Pages. People also use other tools to do syntax highlight. My personal website actually use highlight.js to implement syntax highlight and you will get more languages support and more themem styles although the usage is quite simple as well, embed its CSS file into your web page.